In vivo biostability of a polymeric hollow fibre membrane for cell encapsulation

The biostability of poly(acrylonitrile-co-vinyl chloride) (P(AN/VC)) hollow fibre membranes was assessed in the rat peritoneal cavity over a 12 month period. The mechanical and chemical stabilities of the hollow fibre membrane (HFM) were characterized by measuring its tensile strength and molecular weight (by gel permeation chromatography) pre-implantation and post-explantation. The stability of the HFM transport properties was determined by molecular weight cut-off (MWCO) and hydraulic permeability (HP). Explanted HFMs were treated with 4 M NaOH to remove adsorbed protein before measuring mechanical, chemical and transport properties. The HFM was stable in vivo for at least 12 months: (i) weight average molecular weight (Mw) at t = 0 was 143,000 g mol-1 (with a polydispersity index (PDI) of 2.3) and at t = 12 months it was 128,000 g mol-1 (with a PDI of 2.8); and (ii) tensile strength at t = 0, 52 +/- 2 mdyne, did not change significantly over time and was 46 +/- 7 mdyne at t = 15 months (P > 0.05 by a two-tailed Student's t-test); and (iii) no significant differences, with respect to standard deviation, were observed in the transport properties: HP was 7.4 +/- 1.5 ml min-1 m-2 mmHg-1 at t = 0 and 7.5 +/- 1.5 ml min-1 m-2 mmHg-1 at t = 12 months, while MWCO (at 90% rejection) was initially 40,000 +/- 8000 g mol-1 and then 54,000 +/- 10,000 g mol-1 at t = 12 months.